Thermoresponsive Terpolymers Based on Methacrylate Monomers: Effect of Architecture and Composition

A series of amphiphilic thermo responsive copolymers was synthesized by group transfer polymerization. Seven copolymers were prepared based on the nonionic hydrophobic n-butyl methacrylate (BuMA), the ionizable hydrophilic and thermo responsive 2-(dimethylamino)ethyl methacrylate (DMAEMA) and the nonionic hydrophilic poly(ethylene glycol)methyl methacrylate (PEGMA). In particular, one diblock copolymer and six tricomponent copolymers of different architectures and compositions, one random and five triblock copolymers, were synthesized. The polymers and their precursors were characterized in terms of their molecular weight and composition using gel permeation chromatography and proton nuclear magnetic resonance spectroscopy, respectively. Aqueous solutions of the polymers were studied by turbidimetry, hydrogen ion titration, and light scattering to determine their cloud points, pK(a)s, and hydrodynamic diameters and investigate the effect of the polymers' composition and architecture. The thermoresponsive behavior of the copolymers was also studied. By increasing the temperature, all polymer solutions became more viscous, but only one polymer, the one with the highest content of the hydrophobic BuMA, formed a stable physical gel. Interestingly, the thermo responsive behavior of these triblock copolymers was affected not only by the terpolymers' composition but also by the terpolymers' architecture. These findings can facilitate the design and engineering of injectable copolymers for tissue engineering that could enable the in situ formation of physical gels at body temperature. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 775-783, 2010